The hobby of fish collecting is one of the fastest joining recreational activities in the United States and Canada with increasing numbers of relatively affluent people joining each year. The enjoyment of salt water fish, with their exotic coloring and shapes, particularly appeals to both men and women.
In fish aquaria used by professional fish breeders and pure hobbyists, it is desired to establish and maintain an environment that is not only habitable for the fish, but is as close as to the native environment in which the fish would live in nature. This is particularly important for salt water fish, many are from relatively pristine environments and most particularly important for the breeding of fish. Even a small amount of environmental stress, including water temperature and contamination, will prevent successful breeding for many species.
While an aquarium soon after being set up and filled with salt water and biological chemicals usually has a suitable environment, if the water is carefully prepared and properly tested, organic wastes, such as left-over food, fecal and other fish-like excretions, and decaying play/animal materials, are introduced over time into every aquarium. These wastes then break down through microbe action. Many of these decaying products create chemical imbalances and become harmful, particularly to certain exotic fish and live rock species that are common and/or popular among salt water aquarium owners. Waste is also unsightly and detracts from the fish viewing experience by an increased rate of algae growth. If the waste is not removed or transformed into a less toxic substance, an aquarium environment quickly degrades as the concentration of contamination climbs until it will either no longer support fish life or does so only in a very degraded or unsightly state.
In the past, fish collectors solved the waste build-up problem by replacing a significant portion of the aquarium water at frequent regular intervals, a laborious time consuming practice impractical for most hobbyists who have other business and jobs. Accordingly, today aquarium water is most often circulated through purifiers or filters, which remove the waste from the water which is then recirculated back into the aquarium system. The term "filter", as used in the field encompasses any device that removes undesirable substances from the aquarium or pond water, whether dissolved organic substances, solid, semi-solid or non-solid particulates, or inorganic contamination.
There are many types of filters available in the consumer market that operate on the basic principle of circulating water from the aquarium through the filter medium, either mechanical or biological, and then pumping the cleansed water back into the aquarium. The medium in these filters is usually a medium for removing solid particles, e.g. floss, or a substance, such as activated carbon, that removes non-solid substances such as dissolved gasses and chlorine, or biological filtration which breaks down waste by a natural biological breakdown process of running the water through biological collecting surfaces. A popular filter material used in mechanical filtration is activated carbon or charcoal, which acts, in particular, to remove both undissolved matter and dissolved matter right from the start. Fine granulated so-called gas grade charcoal has an adsorptive surface on which chemicals of all descriptions may be adsorbed.
In filtering water in a fish tank, it is best to skim the water from the surface of the tank. Most waste and debris found in a fish system are protein based and float to the top of the tank with air bubbles, especially if air or water circulation pumps are used in the tank. In common practice the filter is basically a device designed to hang onto the top edge on the side of the fish tank with a part of the device inside the tank. The filter system sucks in water from the tank taking in water that contains the most dirt and protein. At the same time the filter system's output is pumped out back into the aquarium. Various filter media such as cotton and carbon or a filter cartridge can be put into the box to achieve very effective mechanical filtration of the water that flows through it. Ordinary coarse filter material such as synthetic filter floss pads of various types can cope with the above if the filter is frequently replaced and cleaned.
For more complete background, the main toxic material produced by the breakdown of excreta, uneaten food, etc., is ammonia. This is converted to nitrates by bacteria, then by further bacterial action, the nitrites are converted to nitrates. Both ammonia and nitrites are harmful to fish, even in minute amounts (250 to 300 parts per million), and can be monitored by suitable test kits. However, if bacteria growth is not present, and filtering not efficient, decomposition of uneaten food and algae produces toxic substances which may kill the fish, coral and live rock.
The most popular commercial fish filter used for both salt and fresh water primarily fresh water aquariums is commonly called a hang-on power filter (see FIG. 2 discussed hereafter for a typical configuration). This type of filter hangs on the top edge of the side of the outside of the back of the tank (somewhat hidden from view). The U-shaped hose, often called a siphon water intake tube, siphons water into the hanging filter container, the electric pump at the bottom of the container keeps this flow going. The water then overflows from the container back into the primary tank. As the water flows out of the output, it passes through filter media contained in the container. These types of filter devices are not suitable for larger fishtanks because they perform only mechanical filtration (no biological function), they do not filter the surface water and are not able to be connected to feed other filtration devices.
This container in most aquariums is a box which is positioned largely outside the aquarium. The device is positioned on the back wall of the aquarium where it cannot be directly seen by an observer. The box itself is usually made of plastic, often transparent or semi-transparent. A portion of the box contains filter material, wool, charcoal or mixture thereof.
Another form of filtration device which is often used in conjunction with the above mentioned salt water systems is called a protein skimmer. Organic waste material formed by aquatic life waste, uneaten food and dead plant tissue is in the fish tank field designated as "protein." In general protein skimmers use air bubbles through a passage column containing aquarium water. Bubbles by surface action carry the protein to the top of the skimmer apparatus where they are periodically removed by "skimming" or overflowing into a reservoir cup of the surface water. Most protein skimmers are costly and complicated and can require frequent adjustment of air and waterflow and emptying of the reservoir cup to prevent overflowing and optimize performance as chemical changes occur in the water from day to day.
Several companies have designed new types of protein skimmers that now hang on the side of the tank. These hang-on designs are intended to eliminate the need of an external filtering tank. The biggest worry and potential problem with a hang-on skimmer is the fact that subtle changes in the chemical make up in the water (such as temperature changes, over feeding or the addition of chemicals) can cause the bubble and dirt collector cup to start to overflow in many cases, all over the floor surrounding the aquarium. With one method currently available for feeding waterflow to this type of skimmer a powerhead pump is submersed well below the surface of the water level of the tank, its failure can result with the owner waking up, or coming home, to find half or more of the tank's water overflowed onto the floor.
As shown in the description above and as discussed hereafter, the most common power filters usually hang outside the top of the aquarium tank. These types of filters are started by filling the external box with water, then the siphon tube is started manually by detaching it and submersing it, holding one's finger over the ends to retain the water, then quickly attaching it back in place. The electric pump is then turned on to start and keep the flow going. A siphon tube conveys water into the filter using a pump inside the filter box to keep the flow going. In such filters, the tube is primed with water by submersing and holding one's thumb over the end and filling the box with water. The water is drawn into a tube by a circulation pump in the box and returns to the tank, while one or more siphon tubes convey water from the tank to the filter, where it passes through the filter bed (or beds) and then is conveyed back into the tank.
While there are numerous patents in the field, see for example recent U.S. Pat. Nos. 5,618,428 and 5,628,905, the most common prior commercial art is summarized below in the discussion of the Drawings.